Device and method for acquiring position with a confocal Fabry-Perot interferometer

Abstract

Device and method for acquiring position with a confocal Fabry-Perot interferometer. In a general aspect, the device for acquiring position may include an arrangement for acquiring position where the acquiring arrangement has a confocal Fabry-Perot interferometer. In another general aspect, a method for acquiring position may include generating an interference pattern dependent on a position of an object by a confocal Fabry-Perot interferometer; detecting the interference pattern to obtain a measuring signal; and evaluating the measuring signal.

What is claimed is: 
     
       1. A device for acquiring a position, comprising:
 a confocal Fabry-Perot interferometer, the confocal Fabry-Perot interferometer including a first resonator reflective surface, a second resonator reflective surface, and a folding reflective surface arranged in a beam path between the first and the second resonator reflective surfaces, the first and second resonator reflective surfaces being provided in a fixed position relatively to one another independent from the position to be acquired, the first resonator reflective surface comprising an exit surface of a core of an optical fibre and the second resonator reflective surface comprising an end surface of an optical part, the end surface being arranged laterally next to the first resonator reflective surface. 
 
     
     
       2. The device of  claim 1 , wherein the folding reflective surface is coupled to an object. 
     
     
       3. The device of  claim 1 , wherein the confocal Fabry-Perot interferometer further comprises:
 a collimator arranged in the beam path between the first and the second resonator reflective surfaces. 
 
     
     
       4. The device of  claim 1 , wherein a reflection factor of the folding reflective surface is more than 0.9. 
     
     
       5. The device of  claim 1 , wherein the folding reflective surface is configured to reflect the beam path from the first resonator reflective surface to the second resonator reflective surface and from the second resonator reflective surface to the first resonator reflective surface. 
     
     
       6. The device of  claim 1 , wherein the first resonator reflective surface is arranged in a radially offset position to the second resonator reflective surface with respect to an optical axis of the beam path. 
     
     
       7. The device of  claim 1 , wherein a finesse of the confocal Fabry-Perot interferometer is less than 1.0. 
     
     
       8. The device of  claim 1 , wherein a first reflection factor of the first resonator reflective surface and a second reflection factor of the second resonator reflective surface are less than 0.15. 
     
     
       9. The device of  claim 1 , wherein a first reflection factor of the first resonator reflective surface and a second reflection factor of the second resonator reflective surface are about equal. 
     
     
       10. The device of  claim 1 , further comprising:
 a light source configured to generate a measuring light; 
 a detector configured to produce a measuring signal; and 
 an evaluation circuit configured to evaluate the measuring signal, 
 wherein the light source is configured to be fed to the confocal Fabry-Perot interferometer, and 
 the measuring signal is generated by the confocal Fabry-Perot interferometer. 
 
     
     
       11. The device of  claim 10 , wherein the measuring signal is an interference pattern. 
     
     
       12. The device of  claim 1 , the device being capable of carrying out a displacement measurement over a measuring range of more than 10-4 m. 
     
     
       13. The device of  claim 3 , wherein the first resonator reflective surface comprises:
 an exit surface of a core of an optical fibre, 
 wherein the optical fibre being connected to the collimator via at least one of a fibre ferrule, a holder, and a housing. 
 
     
     
       14. The device of  claim 1 , further comprising:
 an annular piece having an annular surface, 
 wherein the annular surface is coplanar with an end surface of the optical fibre. 
 
     
     
       15. The device of  claim 14 , wherein at least one of the resonator reflective surface and the annular surface is provided with a spherical shape. 
     
     
       16. An apparatus, comprising:
 a positioner; and 
 the device of  claim 1 . 
 
     
     
       17. A method for acquiring a position, comprising:
 generating an interference pattern dependent on a position of an object by a confocal Fabry-Perot interferometer, the confocal Fabry-Perot interferometer including a first resonator reflective surface, a second resonator reflective surface, and a folding reflective surface arranged in a beam path between the first and the second resonator reflective surfaces, the first and second resonator reflective surfaces being provided in a fixed position relatively to one another independent from the position to be acquired, the first resonator reflective surface comprising an exit surface of a core of an optical fibre and the second resonator reflective surface comprising an end surface of an optical part, the end surface being arranged laterally next to the first resonator reflective surface; 
 detecting the interference pattern to obtain a measuring signal; and 
 evaluating the measuring signal. 
 
     
     
       18. A device for acquiring a position, comprising:
 a confocal Fabry-Perot interferometer, the confocal Fabry-Perot interferometer including a first resonator reflective surface and a second resonator reflective surface, the first and second resonator reflective surfaces being housed in a same structural unit, wherein the first resonator reflective surface and the second resonator reflective surface abut one another.